The present invention relates to materials for semiconductor device assemblies. More particularly, the present invention relates to interconnection systems between a semiconductor device or "die", sometimes referred to as a "chip", and substrates that employ interconnections in the form of "bumps", sometimes referred to as "controlled collapse chip connections" or "flip-chip" technology. The invention also relates to compositions for use as an underfill, as an encapsulant, as a dam, as a die attach adhesive and as an electrical connection for a semiconductor device.
Conventional semiconductor device packages or die attach systems generally involve adhering a die to a substrate with a die attach adhesive followed by wire bonding of the die or chip to the package to establish electrical connections. A hermetic package is then formed by sealing a lid to the substrate to hermetically seal the die in the package. However, as the complexity of semiconductor devices is increased and require larger number of electrical connections, the wire bonding step becomes a bottleneck in the manufacture of semiconductor devices as microprocessors.
Controlled collapse chip connections or flip chip assembly is seen as a way to avoid wire bonding and to facilitate manufacturing processes. By this technique, the semiconductor device is attached to a substrate using solder balls applied to the semiconductor device during the chip manufacturing process and the solder balls are then aligned with solder "bump pads", on the substrate prior to heating to elevated temperatures to cause solder flow and establish the interconnection. This technique enables more rapid continuous manufacturing of semiconductor assemblies and enhances the durability of the semiconductor device by decreasing the resistance and heat generation throughout the life cycle of the device.
One difficulty encountered in using the flip chip technology is that as the number of inlets and outlets (I/O), i.e., interconnection pins, bumps, etc., increases, the attachment or depositing of solder bumps to the semiconductor chips becomes more expensive. Screens or stencils with appropriate pattern and geometry can be used to print electronically conductive, low temperature thermostable paste of polymeric material onto a silicon wafer to provide thousands of bumps more economically in a short time. The uncured bumps can then be attached to the substrate followed by curing to form electrically conductive polymeric interconnections to replace the traditional solder bumps. However, although such polymeric interconnections function well, they are subject fatigue problems and lack durability as a result of the heating and cooling cycling of the semiconductor device as the microprocessors in which they are used are turned on and off. The present invention substantially reduces the stress on the semiconductor device interconnection, significantly increases durability, even when subjected to heating/cooling cycles, and improves moisture resistance.